Method for making a pyrotechnic device

ABSTRACT

A FLARE BODY FOR A PARACHUTE TYPE FLARE PROVIDING SUPERIOR BRILLIANCE AND SUSTAINED OUTPUT OF ILLUMINATION EVEN AFTER 14 DAYS OF O24 HOUR TEMPERATURE CYCLING BETWEEN -65 AND 165*F. IS OBTAINED BY MEANS OF A NOVEL, CASTABLE ILLUMINANTT FLARE COMPOSITION COMPRISING AN UNCURED, HIGH OXYGEN CONTENT LIQUID PLYMERIC BINDER MATERIAL, PARTICULARLY A LIQUID SATURATED POLYESTER POLYMER/ LIQUID EPOXY RESIN SYSTEM, WHICH IS LOADED INTO A FLARE BODY CASING LINED ON ITS INNER BOTTOM AND SIDE SURFACES WITH AT LEAST PARTIALLY CURED LINER MATERIAL COMPRISING THE BINDER MATERIAL AND FURTHER COMPRISING AN ANCHOR SHEET MATERIAL BONDED COMPLETELY ON ITS INNER SURFACE TO THE OUTER SURFACE OF THE LINER AND ON ITS OUTER SURFACE TO THE INNER CASING WALL ESSENTIALLY ONLY BY A RELATIVELY NARROW ANCHOR STRIP OF MATERIAL RUNNING FROM THE TOP TO THE BOTTOM OF THE CASING. THE LOADED CASING AND ITS CONTENTS THEN ARE HEATED TO CUURE THE POLYMERIC BINDER MATERIAL IN THE COMPOSITION, LINER AND ANCHOR STRIP.

May 29, 1973 v, Dl SD ET AL 3,736,206

METHOD FOR MAKING A PYROTECHNIC DEVICE Original Filed Feb. 10, 1969 3 Sheets-Sheet l R Y To A j V I I Fig.l Fig.2

Robert E Meyer Vern Thomas Dinsda/e Russell Reed; r mvsmoxs May 29, 1973 v. DINSDALE ET AL 3,736,206

METHOD FOR MAKING A PYROTECHNIC DEVICE Original Filed Feb. 10, 1969 3 Sheets-Sheet 2 w .4 M b m m m ZOPCwOQEOU 22mwm0Z I $35235 A 55% 5:8 MEEUE 2 xi 29.55 3552 9 zoEwomzou main 9 S8 zmmmuw FEE. z ll 55.235 mom #2.: U260 96.5 Al 82.5 A 2:53 mEmBmmwz. 20....6228 E5: 2 3 8 NEE QUE -25 9E3 =15 @0192 0 5m: 2 AI. 3 2w: 2a mmzw mo=uz Ez: E3 8 km: 2.282% 0:58 592 e @263 $2: at: aw wimw 225228 20:69.28 ZOE-58200 AL mm w IOIOZ Jim-E42 KHZ-J V JSENPdZ mmzj 55.23 Q43 mmEmE 8 xi m8 $5.312. @5936 L 20.58 4.23 $253 38 main. M562. 8 zoEmo fizz 9555 A nhwmwwmmwwm @255 A28 E2. 3&2 x262 5&2

Vern Thomas Dinsda/e Russell Reed, Jr.

INVENTORS y 1973 v. T. DINSDALE ET AL 3,736,206

METHOD FOR MAKING A PYROTECHNIG DEVICE Original Filed Feb. 10, 1969 5 Sheets-Sheet 3 I 0 O N o 0 [LI E rb 0 l0 0 o m o m o (\i owazmodznclrwo Robe" 5 Meyer Vern Thomas Dinsda/e Russell Reed, Jr

INVENTORS United States Patent 3,736,206 METHOD FOR MAKING A PYROTECHNIC DEVICE Vern Thomas Dinsdale and Russell Reed, Jr., Brigham City, and Robert E. Meyer, North Ogden, Utah, assignors to Thiokol Chemical Corporation, Bristol, Pa. Original application Feb. 10, 1969, Ser. No. 797,906, now Patent No. 3,605,624. Divided and this application May 18, 1971, Ser. No. 144,680

Int. Cl. B32b 29/00; C06d N10 US. Cl. l56--293 4 Claims ABSTRACT OF THE DISCLOSURE A flare body for a parachute type flare providing superior brilliance and sustained output of illumination even after 14 days of 24 hour temperature cycling between -65 and 165 F. is obtained by means of a novel, castable illuminant flare composition comprising an uncured, high oxygen content liquid polymeric binder material, particularly a liquid saturated polyester polymer/ liquid epoxy resin system, which is loaded into a flare body casing lined on its inner bottom and side surfaces with at least partially cured liner material comprising the binder material and further comprising an anchor sheet material bonded completely on its inner surface to the outer surface of the liner and on its outer surface to the inner casing wall essentially only by a relatively narrow anchor strip of material running from the top to the bottom of the casing. The loaded casing and its contents then are heated to cure the polymeric binder material in the composition, liner and anchor strip.

This application is a division of copending application Ser. No. 797,906 filed Feb. 10, 1969, now Pat. No. 3,605,624.

CROSS-REFERENCE TO RELATED APPLICATION A parachute-type illuminating flare in which the illuminant flare body of the present invention may be used is disclosed and claimed in copending application Ser. No. 787,079 filed Dec. 26, 1968, now US. Pat. No. 3,593,664.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to high intensity relatively prolonged burning time, parachute-type illuminating flares, particularly of the type used in military operations. The invention more particularly relates to the composition of the illuminant grain and to the method by which the illuminant grain is retained in the flare body casing.

Desciption of the prior art Castable pyrotechnic compositions comprising a polymeric binder are known. Such compositions are taught, for example, in Us. 2,700,603, in which to 40 percent of .a liquid plastic of the group consisting of polyfunctional mercaptans, polyesters and dichlorostyrene catalyzed with peroxides or tin compounds is used for the binder and cured at room temperature.

Casing bonding of castable pyrotechnic compositions to a casing liner bonded to the casing also is known and is taught, for example, in US. 3,212,256, in which a liner of a thermoplastic material, particularly polyurethane rubber, is cast to the inner wall of a rocket and the propellant grain of the rocket is bonded to the liner by means of a unique surface preparation, namely, methyl-a-cyanoacrylate containing sulfur dioxide.

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SUMMARY OF THE INVENTION The present invention is directed to providing an improved illuminating flare body which will provide intensely brilliant light for at least several minutes while suspended by parachute in aerial applications such as for aerial photography and military missions. Since such flares must be ready for instant use at various air densities under a wide variety of temperature and climate conditions which cause expansion and contraction of the flare casing and grain and must withstand transportation shock and vibration forces in ground and air vehicles, the physical integrity of the illuminant composition must be such that the composition will not crack, pulverize or otherwise develop flaws which will cause the flare to function erratically or to fail to function. For example, the expansion and contraction of the illuminant composition in its casing due to temperature changes, which may range from about 65 to F., may cause the illuminant composition, or grain, to pull away from the liner which is normally used in pyrotechnic devices such as flares and rockets. In such an event, the grain may burn along the side of the grain causing a side-burning eflect which considerably shortens the burning time of the flare. Furthermore, the casing, which, in a flare of the type described herein, is usually made of aluminum metal or magnesium metal or one of the alloys of such metals, usually has a different coefiicient of expansion from that of the liner and of the grain, and the liner may have a different coeflicient of expansion from that of the grain. Also, in rarified atmospheres, the oxygen content of the air will be less than that at ground level and will adversely affect the burning rate of the grain if the ingredients of the illuminant composition must depend on oxygen from the air to sustain their combustion. Positive ignition of the grain under all the temperative conditions that may be encountered in arctic as well as temperate and tropical temperature zones also must be obtained by the illuminating flare. The amount of light intensity which may be obtained during burning of the flare is still another, and most important objective to be attained. This factor can be expressed in candlepower per second per gram of grain, and the higher this factor the better the illuminating efiiciency of the flare.

The objects of the invention, as well as other advantages and benefits are obtained by means of novel, castable flare illuminant composition comprising an uncured, high oxygen content polymeric binder material which is loaded into a flare body casing lined on its inner bottom surface and on its inner wall surface with liner composition material comprising the above binder material and having at least its grain-facing surface cured only to a tacky state, the liner, preferably, in turn being bonded to a second cured or partially cured layer of the same liner ma,- terial further bonded to an anchor sheet of combustible sheet material, the latter material being bonded by means of an uncured layer of the liner material by its back surface, along a relatively narrow anchor strip running parallelly to the long axis of the casing, to the inner wall of the casing. The loaded flare body casing is then heated to cure all the illuminant grain, liner and anchor strip.

The illuminant flare when made according to the inyention and assembled into an aerial type flare withstands shock and air transport vibration after 24 hour temperature and cycling for 14 days at temperatures in the range of 65 to 165 F. It functions properly when deployed from an aircraft at an elevation or several miles and provides as much as 50,000 candlepower per second per gram of grain.

The high oxygen content polymeric binder used in the practice of the invention preferably is a binder system comprising a liquid saturated polyester polymer havinga carbon to hydrogen to oxygen ratio of about 222.5:1 and having a viscosity at 25 C. of about 450 to 550 poise mixed with a liquid epoxy resin having a viscosity at 25 C. of about 500 to 900 centipoise.

The method of case bonding of the liner comprises bonding the liner to a sheet of combustible material, preferably a thin sheet of Kraft process paper, and then bonding the sheet along a narrow strip of its outer surface to a narrow strip of liner material, referred to herein as an anchor strip, bonded to a corresponding area of the casing inner wall. Bonding of a portion only of the sheet only to a portion of the casing wall rather than bonding the entire sheet to the entire inner wall surface of the casing, permits the liner and illuminant grain to expand and contract independently of the casing while still being firmly held by the anchor strip in the position in which it is placed in the casing during assembly and during burning.

On ignition and during burning of the flare, the endsurface of the grain, of the liner, of the sheet material and of the casing burn away at substantially the same rate. Because of the efficiency of the bonding of the liner to the grain, side-burning does not occur, as might occur if the liner-to-grain bond were defective.

BRIEF DESCRIPTION OF THE DRAWING The cast flare illuminant and its method of manufacture are illustrate in the drawing wherein:

FIG. 1 is a fragmented view of the illuminant flare body showing the cured illuminant with portions of the casing wall, anchor strip, anchor sheet, liner and illuminnant composition cut away to show the arrangement of these parts;

FIG. 2 is a cross-sectional view of the illuminant flare taken along the line 22 of FIG. 1 and additionally showing the bottom liner relative to the other parts;

FIG. 3 is a process diagram depicting the various steps of the assembly operations; and

FIG. 4 is an illumination output trace of an illumination flare made according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The illuminant flare of the present invention in its preferred embodiment may be better understood from the drawing. In the drawing, FIGS. 1 and 2 illustrate the construction of the flare, FIG. 3 illustrates the method of constructing the flare, and FIG. 4 illustrates the candlepower output of an 18 inch flare of about 4.65 inch diameter.

Referring to FIGS. 1 and 2, the illuminant flare 1 comprises a casing 2, preferably of aluminum, to which is bonded a strip 3 of cured liner composition material, further described below. A thin layer of combustible anchor sheet 4, preferably Kraft process paper, is shown bonded, preferably along its overlapped seams, to an anchor strip 3 of cured liner composition. A side liner 5 of cured liner composition material is shown bonded to the complete inner wall of anchor sheet 4. A bottom liner 6 of cured liner composition material is shown bonded directly to the inner bottom wall of the casing 2. Cured illuminant composition 7 is shown bonded directly to the side liner 5 and the bottom liner 6. The illuminant compositioned 7 is loaded into the lined casing so that its top, as shown, is sufliciently below the open end 8 of the easing 2 to provide room for insertion and support of ignition means, not shown. The illuminant flare body 1 substantially in the form shown is ready for assembly into a parachute-flare of the type described in the copending application, above.

The method of constructing the illuminant flare 1 in a preferred embodiment is illustrated in FIG. 3 taken in conjunction with FIGS. 1 and 2. An aluminum casing 2 of thin wall construction for the illuminant composition is degreased and abraded to prepare it for application of a strip 3 of fiowable uncured liner composition to the casing.

The fiowable uncured liner composition preferably is prepared by homogenously blending together in a dry atmosphere the ingredients showing in Table 1 in about the proportions listed there.

TABLE l.LINER COMPOSITION Parts by weight Ingredients Preferred Range The uncured liner composition preferably has a viscosity of a thick syrup. It may be applied to the inner wall of the casing 2 by means of a brush or roller to form the anchor strip 3 by running the brush or roller from the bottom of the casing to the open end thereof, forming an anchor band of suflicient width and thickness to hold the anchor sheet 4 and liner 5 in place when the latter items are inserted into the casing, as described below. Preferably, in a casing 2 having an inner diameter of about 4 to 5 inches, the anchor strip 3 will be about 2 to 3 inches in width. While a wider anchor strip may be used, it should not be so wide that the purpose of the strip, i.e. providing for expansion-contraction movement of the casing 2 about the lined illuminant composition 7, would be defeated. The anchor strip 3 need have a thickness at least sufficient to bond the anchor sheet 4 to the casing 2. Usually a thickness of several thousandths of of an inch will be adequate. The anchor strip 3 may be semi-cured by heating the casing to about F. for about 24 hours.

The uncured liner composition is also used to coat one side of anchor sheet 4 material, which preferably is in the form of a continuous roll of the material having a width of about the depth of the inner wall of the casing, by applying the composition to the sheet by brush or roller means. However, the composition is preferably applied in the form of a solution or suspension of the composition in an organic solvent, e.g. methylene chloride, by spraying the solution onto one surface, preferably the top surface, of the sheet as it is unrolled, and evaporating the solvent.

The anchor sheet 4 provides a convenient means for controlling the overall thickness of the liner 5, which itself serves as the principal side-burning inhibitor and shock insulation means for the illuminant composition 7 in the manner, e.g., well-known in the rocket propellant art. The combination of the anchor sheet 4 and the liner 5 should be suflicient in thickness to provide adequate inhibiting and insulation of the illuminant composition 7 grain over the temperature range from about 65 to 165 F. under conditions of mechanical shocks and vibration of transportation both on ground level and in the air. The combination should be of minimum thickness for the above purpose in order to be able to provide maximum light output per cross-sectional area of the flare 1. Also, its oxygen requirements for combustion purposes should not be dependent on the illuminant composition 7, but should be self-contained. The ingredients of the liner composition 5 of Table 1 contain suflicient oxygen for this purpose. The thickness of the Kraft process paper anchor sheet 4 material thus may be about 0.005 to 0.010 inch, and the thickness of the liner about 0.015 to 0.05 inch to provide a satisfactory combination of liner-anchor sheet.

The uncured liner composition material is built up on the anchor sheet 4 to about the desired thickness and then is cured by heating to about F. for about 24 hours. The cured liner surface is then given a second coating to build up the remainder of the desired thickness and the second coating is partially cured by heating at about 100 F. to a tacky state only. The liner-anchor sheet combination is cut to a length somewhat greater than the inner circumference of the casing, preferably being sufliciently greater in length to provide an overlap of the ends of about A to 1 inch. The cut liner-anchor sheet is then wrapped around an expandable mandrel having an outer diameter such that when the sheet and mandrel are inserted into the casing, the mandrel can be expanded to press the liner-anchor sheet snugly against the inner wall of the casing. The overlapped seam 9 preferably is positioned so that it seats against the anchor strip 3 and adheres there to the uncured liner composition of the strip. The surface of the mandrel preferably is coated with a synthetic resin, e.g. polytetrafluoroethylene, which is non-adherent to the tacky surface of the liner 5.

The inner bottom of the casing 2 is next lined with a layer of the uncured liner composition to form a shock and vibration insulator bottom liner 6. The thickness of the liner 6 is about the same as the thickness of the lineranchor sheet combination.

The lined casing 2 is now ready for loading with uncured illuminant composition 7. The composition 7 is a flowable mass prepared by homogeneously mixing the ingredients shown in Table 2 in about the proportions listed there.

TABLE 2.ILLUMINANT COMPOSITION The mixing of the illuminant composition ingredients of Table 2 is carried out in a dry inert atmosphere to avoid moisture pickup. Preparatory to the mixing, the sodium nitrate is ground, if necessary, and screened to provide a medium-sized fraction of particles averaging about 150 microns in cross-section and a fine-sized fraction of particles averaging about 5 microns in cross-section. The two fractions then are blended in the ratio of F. for about 48 to 72 hours and/or until cured to a Shore C hardness value of 40 or higher.

Typical physical and performance properties of the cured illuminant grain ambient (75 F.) temperatures are shown in Table 3.

TABLE 3 Physical and performance properties of illuminant flare Modulus, p.s.i 7,600 Maximum stress, p.s.i 150 Strain at cracking, in./in. 0.03 Strain at maximum stress, in./in. 0.03 Cured density, gm./cc. 1.57 Shore C hardness 40 Adhesion of grain to liner tensile cup adhesion, p.s.i.:

at 65 F. 196

at F. 48.5

at l65 F. 14.5 Rate of burning, in./sec. 0.087-0.092 Illumination output, cand1epower/sec./ gm. 50,000

The cured illuminant composition in the lined casing 2 is herein referred to as a flare body 1. After the curing step, the flare body 1 is cooled and then is conveyed to a flare assembly station where it is fitted with ignition means and other components for deployment as a parachute-type illumination flare.

Flare bodies made according to the invention were subjected to, and successfully passed, the requirements of the following tests:

(1) Temperature conditioning MIL-STD-331, Item at -6S F. for 24 hrs. and 165 F. for 24 hours.

(2) Temperature cycling for 14 days at temperatures ranging from -65 to 165 F.; MIL-STD-331, 'Item 105.

(3) Aircraft vibration requirements MILE5272C, Item 12.

(4) Transportation vibration requirements MIL-STD- 331, Item 104.

Test results obtained on burning illumination flares made according to the present invention as compared to flares made by the prior art method, which involved high pressure, press loading techniques, such as those described in US. 2,700,603, are shown in Table 4. The tests were made with flares loaded into a casing 2 containing a grain measuring 18 inches in length and 4625:0031 inch in diameter.

TABLE 4.ILLUMINANT FLARE TEST RESULTS Average Efficiency is out ut e sec.

Flare number Conditionin test temperature (see.) sec.) 0%. /m.)

Ambient/ambient 175 0. 093 1. 60x10 38, 500

Pressed (01d) o 176 o. 092 1. 63X10 39, 500

1/1 (new) Aircraft vibratmn/ambient 206 0.087 1. 86X10 42,000

1/2 (new) Transportation vibration/ambient 207 0.087 1. 95x10 54, 400

1].) (new). Ambient/ambient 190 0. 091 1. 83X10 49, 400

1/6 (new)-- 14 day temperature cycling/ambient- 194 0. 089 1 90 10 52, 000

Average:

Old 175.5 0.0925 1. 615X10 39, 000

New 199. 2 0. 0885 1. 885x10 52, 075

Percent change new/old. 13. 5 4. 4 16. 7 33. 5

No'rn.t|,=time of burning, seconds; rs,=rate of burning, inches/seconds; cp.=candlepower.

about 1 part medium-sized to 2 parts fine-sized particles before adding to the mixer. Mixing is carried out for about 20 to 30 minutes in a known manner in the temperature range of i5 F. in accordance with the usual safety practices.

The mixed uncured illuminant composition is a flowable crumbly mass. The mass is fed by a conveyor to a loading station where it is loaded in increments into the lined casing 2. Each increment is tamped into place with a pug type tamper to obtain a densely packed load free of voids and crevices. The mixture has a pot life of about 8 to 24 hours at 60 to 100 F. and can readily be handled without danger of premature set-up.

The loaded casing 2 is conveyed to a curing room an subjected to a curing temperature of about to 75 shown in-Table 5.

The test data show that compared to the prior art pressed illuminant flare the novel illuminant flare of the present invention, even after being subjected to all the stringent test conditions described above, has (a) a burning time which is 13.5% longer, (b) a burning rate which is 4.4% slower, (c) a candle-power output which is 16.7% greater, and (d) an efficiency, measured as candlepowers of output per second per gram of grain, which is 33.5% higher. Therefore, it is seen that the invention provides a highly superior illuminant flare and a-method for its manufacture.

The thermal coefficient of expansion of the illuminant grain compared to that of the aluminum of the casing is 7 TABLES THERMAL COEFFICIENTS OF EXPANSION Coefficient of linear Temperature range: expansion cm./cm./ C.

Casing: 100 to +100 C. 240x10- Grain: -100 to 29 C 273.6 l" Grain: -29 to 0 C 408.0 10* Grain: 0 C. to 100 C. 544.6 10- The data in Table show that the linear coefficient of expansion of the grain is from 113 to 226% greater than that of the casing. The adverse effects of the above great difierence in relative amounts of linear expansion, and conversely, of contraction are overcome by the method of construction and the structure of the illuminant flare in accordance with the invention.

FIG. 4 illustrates a typical illumination output trace for an illuminant flare made according to the invention and used in carrying out the above tests. The trace represents the illumination output obtained while burning a flare on a test tower 67 feet above ground level. The average illumination produced was 1.79 candlepower, which is about equivalent to 1.97 to 2.01 10 candlepower in a photometric tunnel.

While specific ingredients have been used to describe and illustrate the invention, it is to be understood that other ingredients having equivalent properties may be substituted for those shown in order to practice the invention and to obtain the benefits and advantages thereof.

The liquid polymeric binder material used in practicing the invention preferably is a mixture of liqud saturated polyester polymer and liquid epoxy resin. Preferably, the liquid saturated polyester polymer is a carboxylterminated polyester polymer such as a carboxyl-containing low molecular weight, aliphatically saturated, substantially completely condensed, polymeric polyester of a saturated aliphatic diol, a dicarboxylic acid free from ethylenic unsaturation, and a polyfunctional compound free from ethylenic unsaturation and containing at least three functional groups selected from the group consisting of polyols, polycarboxylic acids and polycarboxylic acid anhydrides, said polymeric polyester being liquid at a temperature between about 25 and about 50 C., having an acid content between about 0.1 and about 1.5 milliequivalents per gram, an average of between about 2.5 and about carboxylic groups per molecule, an average molecular weight between about 700 to about 10,000 and free from hydroxyl groups. Such polymers are known and are taught, for example, in US. 3,182,- 041, incorporated herein by reference. Preferred liquid saturated polyester polymers are those having a high oxygen content combined with the carbon and hydrogen content of the polymer. Especially preferred are liquid saturated polyester polymers having a carbon to hydrogen to oxygen ratio of about 2 to 2.55 to l and a viscosity at 25 C. of 4 80 to 520 poise. Polyesters prepared from saturated diacids, e.g. saturated fatty acids, such as succinic and glutaric acids and their anhydrides, are especially preferred.

Liquid epoxy resins and solutions thereof are also well-known. The epoxy resins are formed by the reaction of a 1,2-epoxy compound and a dihydric phenol. The preferred 1,2-epoxy resins are prepared by the reaction of epichlorhydrin with Bis-Phenol-A (2,2 bis-(4-hydroxyphenyl)-propane), generally in alkaline solution. Epoxy resins also are prepared from other 1,2-epoxy compounds including, for example, polyglycidyl ethers of ethylene glycol, propylene glycol, trimethylene glycol, diethylene glycol, triethylene glycol, gycerol, dipropylene glycol, etc. Similarly, other dihydric phenols may be employed, including resorcinol, catechol, hydroquinone, 4,4'-dihydroxybenzophenone, 1,1 bis-(4-hydroxyphenyl)-butane, 1,5-dihydr0xynaphthylene, etc. It is understood that the epoxy resins formed from the various reactants mentioned above are not necessarily equivalent and, furthermore, that the exact composition of the epoxy resins are dependent upon the molecular proportions of the epoxy compound and dihydric phenol employed in its preparation. Preferred liquid epoxy resins are those having an epoxide equivalent (weight of resin in grams containing 1 gram of epoxy) of about 175 to 210 and a viscosity of about 500 to 900 centipoises. When a solvent is used, organic solvents such as toluene, xylene and ketones, e.g. acetone, are preferably used. The liquid epoxy resin serves as a curing agent for the polyester polymer. Polyfunctional epoxy resin is especially preferred, particularly, a trifunctional epoxy resin wherein the functional group is hydroxyl or amino.

While the liquid epoxy resins are preferred as curing agents for the polyester polymer, other polyfunctional curing agents may also be used, for example, polyfunctional aziridines, e.g. trifunctional derivatives of ethylenimine and other alkylenimine derivatives, and other cur ing agents such as those taught in US. 3,182,041, above.

The binder material is accelerated in its curing by the addition of a small amount of catalyst for the curing agent. Preferably, the curing rate catalyst is a metal salt of a fatty acid, e.g. iron linoleate Such compounds are commonly referred to as metallic soaps. They are insoluble soaps of such fatty acids as stearic, naphthenic, octoic or 2-ethylhexoic, rosin (resinates), or tall oil (tallates) with the heavier metals such as aluminum, calcium, cadmium, copper, iron, lead, tin or zinc. Sufiicient catalyst is used to obtain a curing rate which will give a pot life of about 8 to 24 hours. The amount will usually be from about 0.5 to about 0.9 parts per parts of liquid saturated polyester polymer, but may be more or less as found desirable.

Generally, it is desirable that the amount of curing agent used be present in at least stoichiometric amount relative to the polyester polymer, in order to provide complete cure of the polyester polymer. The amount of catalyst used then controls the rate at which the cure occurs.

The cured polymeric binder material whether present in the illuminant composition, in the liners or in the anchor strip should have adequate bonding strength to form a strong bond between the ingredients in the illuminant and liner compositions, and the surfaces to which the cured compositions are bonded.

The magnesium used in the illuminant composition is preferable in a particulate form of metal fuel. While magnesium is preferably used for its white light producing capability, it may be desirable in some cases to use other metals used in pyrotechnic devices as metal fuels in place of some of the magnesium, e.g. aluminum, or magnesium-aluminum and zirconium and their hydrides, cerium and uranium. The metal fuel is preferably used in a ratio of about 5 to 10 parts by weight relative to the polymeric binder material.

Sodium nitrate is preferably used as the oxidizer for the magnesium fuel of the pyrotechnic combination in the illuminant composition. However, in some cases it may be advantageous to use another metal nitrate, e.g., lithium nitrate, taking due precautions in handling the latter because of its greatly hygroscopic nature. When white light is not essential, color producing metal nitrates, such as barium or strontium nitrate, may be used advantageously. The metal nitrate is preferably used in at least a stoichiometric amount relative to the metal fuel ingredient of the illuminant composition.

The anchor sheet 4 material preferably is a thin Kraft process paper. However, the material may also be a sheet form of other material to which the liner composition material will bond. Primarily, the anchor sheet 4 provides an efficient means for controlling the thickness of the liner. It also serves as a. reinforcing cover for the liner.

Additionally, it must have adequate strength to permit it to serve as an intermediate bond between the liner and the anchor strip 3. Furthermore, the anchor sheet material should be combustible so that it will be consumed and not interfere with combustion of the aluminum casing. It is preferred that all the flare body components be consumable so that no danger is created b'y falling debris from the burning flare. Accordingly, other anchor sheet materials include linen or cotton webbing, combustible synthetic plastic or resin materials such as polyurethane, polyesters, polyethers, polysulfide ruibber, polyhydrocarbon rubber, e.g. hydroxyterminated polybutadiene rubber, and the like.

In some cases it may be advantageous to eliminate the anchor sheet 4, particularly, when the liner is made by another method than that described above, e.g., by forming it by extrusion means. In such cases, the liner can be made thicker, if necessary, and can be bonded directly to the anchor strip in the manner described above.

The filler materials used in the liner composition material for making the liner 5 and the anchor strip 3 may be one or more materials useful as reinforcing agents in the plastics art, such as carbon black, clays, slate flour, aluminum oxide, silicon dioxide, magnesium silicate, iron oxide and rayon or other synthetic resin or plastic floc. In general a total of from about 50 to 100 parts of fillers will be advantageous for practice of the invention.

Sufficient filler material should be used to reinforce the liner so that it will have sufficient cohesive strength to withstand the shearing and abrasive forces encountered in compacting the illuminant composition into the lined casing while also retaining sufiicient resilience to permit it to absorb shock and vibration and to expand and contract over the entire temperature range to which the illuminant flare may be subjected.

Many modifications and variations of the present invention will be obvious to those skilled in the art of formulating illuminant compositions, bonding resins, and constructing illuminant flares and other pyrotechnic devices. It is therefore to be understood that such other modifications and variations that fall within the scope of the claims hereof are intended to be included therein.

We claim:

1. The method for making a pyrotechnic device having a walled casing for containing pyrotechnic material, said device having improved resistance to adverse effects of forces of contraction and expansion when subjected to temperatures ranging from -65 to 165 F., said method comprising:

(a) degreasing and abrading the inner Wall of said casing;

(b) coating the inner wall of said casing with flowable organic polymeric material so as to form a strip extending from the bottom to the top of said casing wall and covering a portion of the inner periphery thereof;

(0) forming a cylinder of combustible material comprising an anchor sheet, said cylinder having an overlapping seam;

(d) coating the interior surface of said anchor sheet 10 with a flowable uncured organic polymeric material to a uniform thickness of from 0.05 to at least 0.015 inch to form a shock and vibration resistant liner thereon;

(e) curing said polymeric material to a tacky consistency to provide said liner;

(f) inserting said coated anchor sheet into said casing such that the uncoated surface thereof faces the casing wall;

(g) radially pressing said coated anchor sheet against said wall and said anchor strip;

(h) depositing uncured flowable organic polymeric material on the inner bottom surface of said casing to a thickness substantially the same as said anchor sheet polymeric coating;

(i) loading castable pyrotechnic composition comprising said uncured flowable material as the binder therefor into said lined casing; and,

(j) heating the loaded casing to cure the polymeric material comprising said anchor strip, liner and pyrotechnic composition.

2. The method of claim 1 wherein the uncured flowable organic polymeric material is a liquid polymer having a high oxygen content combined with its carbon and hydrogen contents.

3. The method of claim 1 wherein the uncured flowable organic polymeric material is a saturated polyester resin derived from a fatty acid.

4. The method of claim 1 wherein the uncured fioW- able organic polymeric material is a carboxyl-containing low molecular weight, aliphatically saturated, substantially completely condensed, polymeric polyester of a saturated aliphatic diol, a dicarboxylic acid free from ethylenic unsaturation, and a polyfunctional compound free from ethylenic unsaturation and containing at least three functional groups selected from the group consisting of polyols, polycanboxylic acids and polycarboxylic acid anhydrides, said polymeric polyester being liquid at a temperature between about 25 and about 50 C., having an acid content between about 0.1 and about 1.5 milliequivalents per gram, an average of between about 2.5 and about 15 carboxylic groups per molecule, an average molecular weight between about 700 to about 10,000 and free from hydroxyl groups.

References Cited UNITED STATES PATENTS 2,700,603 1/1955 Hart et a1. 260-40 R 2,366,261 1/ 1945 Hitt 10237.8 3,051,085 8/ 1962 Finkelstein 10237.8 3,120,184 1 2/ 1964 Ellern 10237.8 2,455,242 11/ 1948 Dwyer 10237.8

ALFRED L. LEAVITT, Primary Examiner C. WESTON, Assistant Examiner US. Cl. X.R. 

